Gyroscopic measurement method and sensor

Abstract

The present invention relates to a gyroscopic measurement method by means of a sensor (10) comprising a housing (12) and a vibrating element (15) able to vibrate relative to the housing (12) simultaneously according to a direction (x) of a pilot mode and a direction (y) of a detection mode, comprising the control (110) of a first and a second vibration amplitude of the vibrating element (15) according to the directions of the pilot mode and detection mode respectively to a predetermined pilot amplitude (xmax) and detection amplitude (ymax), and the determination (120) of an instantaneous angular speed (Ωmes) of the housing (12).A predetermined bias (ξ(t)) is introduced into a measurement of an angular position (θ) of the direction (x) of the pilot mode used to determine a biased force (Fass,bias) to be exerted on the vibrating element (15) for the control of the first and/or second vibration amplitude, to cause controlled rotation of the direction (x) of the pilot mode in the plane of vibration (XY).

1 . A gyroscopic measurement method by means of a sensor comprising a housing and a vibrating element able to vibrate relative to the housing in a plane of vibration attached to the housing simultaneously according to a direction of a pilot mode and according to a direction of a detection mode different from the direction of the pilot mode, the method comprising the following steps of:
 a) servoing a first vibration amplitude of the vibrating element according to the direction of the pilot mode to a predetermined pilot amplitude, and a second vibration amplitude of the vibrating element according to the direction of the detection mode to a predetermined detection amplitude, and   b) determining an instantaneous angular speed of the housing relative to a sensitive axis of the sensor from measurements of the vibrations of the vibrating element and the pilot amplitude,   the method being characterized in that a predetermined bias is introduced into a measurement of an angular position of the direction of the pilot mode used to determine a biased force to be exerted on the vibrating element for servoing the first and/or second vibration amplitude,   the introduction of the predetermined bias causing a controlled rotation of the direction of the pilot mode in the plane of vibration,   the instantaneous angular speed of the housing being further determined from the predetermined bias.   
     
     
         2 . The gyroscopic measurement method according to  claim 1 , wherein the predetermined bias is configured to cause rotation of the direction of the pilot mode by a predetermined angle alternately in a first direction and in a direction opposite to the first direction. 
     
     
         3 . The gyroscopic measurement method according to  claim 2 , wherein the predetermined angle is equal to 90°. 
     
     
         4 . The gyroscopic measurement method according to  claim 1 , wherein the detection amplitude is chosen to be zero. 
     
     
         5 . The gyroscopic measurement method according to  claim 1 , in which the servoing step comprises:
 a measurement of the vibrations of the vibrating element;   an estimation of a phase characteristic of the vibrations of the vibrating element according to the direction of the pilot mode from the results of the measurement;   a first estimate of a first force the direction of which is the direction of the pilot mode to be exerted on the vibrating element to servo the first amplitude from the results of the measurement and the estimated phase;   a second estimation of a second force the direction of which is the direction of the pilot mode to be exerted on the vibrating element to servo the second amplitude from the results of the measurement and the estimated phase;   introduction of the predetermined bias in the directions of the first force and the second force;   control of the biased force which is equal to the resultant of the first force and the second force after introduction of the predetermined bias in the directions of these two forces.   
     
     
         6 . The gyroscopic measurement method according to  claim 5 , wherein the second force comprises only one component in phase with the vibrations of the vibrating element according to the direction of the pilot mode. 
     
     
         7 . A gyroscopic sensor comprising a housing and a vibrating element able to vibrate relative to the housing in a plane of vibration attached to the housing simultaneously according to a direction of a pilot mode and according to a direction of a detection mode different from the direction of the pilot mode and configured to implement the steps of the method according to  claim 1 . 
     
     
         8 . The gyroscopic sensor according to  claim 7 , comprising:
 a first control module, configured to estimate a first force to be exerted according to the direction of the pilot mode to servo a first vibration amplitude of the vibrating element according to the direction of the pilot mode to a predetermined pilot amplitude;   a second control module, configured to estimate a second force to be exerted according to the direction of the detection mode to servo a second vibration amplitude of the vibrating element according to the direction of the detection mode to a predetermined detection amplitude;   a measurement module, configured to generate measurements of the vibrations of the vibrating element according to two directions of a reference frame attached to the housing, said two directions being contained in the vibration plane;   a command module, configured to determine a biased force to be exerted on the vibrating element to servo the first and/or second vibration amplitude, from the first force and the second force and from a biased angular position of the direction of the pilot mode in the reference frame attached to the housing which corresponds to an angular position of the direction of the pilot mode in the reference frame attached to the housing after introduction of a predetermined bias, and for exerting the biased force;   a bias device, configured to supply the biased angular position to the command module from measurements of the vibrations of the vibrating element according to the two directions of the reference frame attached to the housing and from the predetermined bias, the introduction of the predetermined bias being configured to cause a controlled rotation of the direction of the pilot mode in the plane of vibration when the biased force is exerted; and   a determination module, configured to determine an instantaneous angular speed of the housing relative to a sensitive axis of the sensor from measurements of the vibrations of the vibrating element, from the pilot amplitude and from the predetermined bias.   
     
     
         9 . The gyroscopic sensor according to  claim 8 , wherein the bias device comprise:
 a reference frame change module, configured to generate estimations of the vibrations of the vibrating element according to the direction of the pilot mode and the direction of the detection mode from measurements of the vibrations of the vibrating element according to the two directions of the reference frame attached to the housing supplied by the measurement module and from the biased angular position supplied by a correction module of the bias device;   a phase module, configured to receive as input, estimations of the vibrations of the vibrating element according to the direction of the pilot mode from the reference frame change module and to estimate a phase characterizing a position of the vibrating element according to the direction of the pilot mode at a current date;   a precession module, configured to receive estimations of the vibrations of the vibrating element according to the directions of the pilot mode and of the detection mode from the reference frame change module and the phase from the phase module, and supply as an output an estimated difference between the angular position of the direction of the pilot mode in the reference frame attached to the housing at the current date and a biased angular position previously supplied by the correction module, and   the correction module, configured to supply the biased angular position to the command module from the estimated difference, the correction module comprising:   i) a sum module, configured to add the predetermined bias to said estimated difference; and   ii) a feedback loop toward the reference frame change module, the feedback loop comprising a gain module and an integration module,   the correction module being configured so that the estimated difference converges to a zero value.   
     
     
         10 . A computer program comprising instructions which cause a gyroscopic sensor comprising a housing and a vibrating element able to vibrate relative to the housing in a plane of vibration attached to the housing simultaneously according to a direction of a pilot mode and according to a direction of a detection mode different from the direction of the pilot mode and configured to implement the steps of the method according to  claim 1  to execute the method according to  claim 1 .